DEAR SAM: Instead of painting my house this year, I decided to go with the installation of either aluminum or vinyl siding for the purpose of a tax write-off. I already have aluminum storm windows. My problem is in choosing between the products; also, I don't want to paint anything on the outside again. - J.M.

ANSWER: I am glad this question was asked after April 15th, since you will have more time to deliberate on your preferences.

If you are expecting an "energy credit" for home siding as is available with storm windows, attic insulation, etc., you should consult the IRS locally for its Form 5695. Unless you include some from of insulation on the outside walls such as rigid Styrofoam (FG) or aluminum foil reflective felt these alone can be deducted but not the siding proper; in addition, only 15 percent of the cost is allowed to a maximum of $300.

If your home will require 1,000 square feet of siding, the cost of insulating products will be approximately $330 for Styrofoam and $40 for reflective felt foil, plus the labor in each case. If labor is estimated at $170 and $60, respectively, the tax credit at 15 percent for Styrofoam amounts to$75 and for foil, $15. These are hardly sizable "tax write-offs." The total costs, including the siding, might be added to your property value as a capital improvement, when you are ready to sell the property.

For an evaluation of the respective products, write to Bird and Sons, Inc. E. Walpole, Mass. (vinyl) and Aluminum Products of America, Wellesley Office Park, Wellesley, Mass. (aluminum) for pamphlets.

DEAR SAM: I am considering buying a house that has a loose wrought iron rail from the entrance hall to the second floor. Will the stairs have to be taken apart to tighten the rail? Secondly, the oil burning heater needs a new flange estimated to cost over $150. Can this be repaired for less? - Mrs. H.R.B.

ANSWER: It is likely that the rail is attached with several flanges to the stair treads by means of screws. These screws may have hexagonal bolt-like heads but the oak-tread screw hole have become enlarged and the flanges cannot be tightly fitted to the treads. Although some plastic wood or fiber anchors could refill these holes, I believe that "lead anchors" would provide greater support to the inserted screws.

The oil burner flange is something that only a service man, knowledgeable in oil burner installation, should repair. The estimate, although it may seem high to you, can be more accurately determined later by inquiring of another service man. Meanwhile, it seemed feasible, that the owner of the house should make you an allowance for this repair.

Have you had an appriaser check the house to determine whether other problems have been overlooked? For example, are there any signs of a "wet basement" such as water lines along the walls or floor? Is the attic insulated with 6 inches of fiber glass? What about the roof shingles? If the house is 20 years old, has it had a new one installed recently? Have you examined the plumbing, such as opening and closing the faucets? Do you hear any water-hammer? An appraiser will advise you about these more important problems and others. It will be most advantageous to have one.

DEAR SAM: I occupy a brick duplex. The top floor has a tiled patio, about 12 x 18 feet, under which is my garage. There is no roof over the patio, causing it to be exposed to all the elements. Some of the tiles are broken and much of the grouting has cracked or is even missing in places. Consequently, after snow there is at least half inch of water standing on the concrete garage floor. How can I correct it? - Ms. E.B.G.

ANSWER: Your detailed description has indeed revealed the source of the trouble. Wear and tear of the patio ceramic tiles, such as moving furniture around, undoubtedly caused the cracked grouting and broken tiles no less than the elements.

Since the patio has been effective previously for several years, you may only want to restore the tiles with new ones. Be sure that you clean the base to replace tiles and use a complete layer of cement on exposed surfaces of the patio. I would recommend that you include one part of medusa waterproofing cement with each five parts of portland. The grouting, too, should have the same composition. Your mason, I am sure, will know how to do the job.

For further protection of grouting, you should paint with two coats of Phenoseal Liquid Water-proofing. If your local hardware or lumber dealer doesn't have it, the Washington area distributor is Knoll Co., 10765 Tucker St., Beltsville, Md. 20705